The present invention relates generally to digital receivers, and more particularly, to programmable digital baseband receivers employing programmable complex threshold detectors and threshold interpreters.
A traditional DSP digital receiver employed to process multiple waveforms typically uses detection methods including sampling, A/D conversion and digital signal processing. The traditional receiver typically includes a low noise amplifier followed by an intermediate frequency (IF) downconverter that is fed by a local oscillator. The IF signal output of the downconverter feeds an AGC amplifier whose output is bandpass filtered. In a DSP receiver, the IF signal is fed to a digital signal processor.
The digital signal processor (DSP) processes the output of the bandpass filter and includes an IF to complex baseband converter, and a complex analog-to digital (A/D) converter. For digital communications, the signal is fed to a baseband equalizer, a symbol decision circuit, and a symbol decoder. For symbol rate processing, a symbol synchronization circuit is coupled to the complex A/D, baseband equalizer, symbol decision circuit, and symbol decoder to synchronize the sequential processing of symbols by these circuits. The traditional DSP, digital signal receiver is thus implemented using programmable and selectable baseband threshold elements and simple logic trees.
The waveform specifications that determine the details of the DSP-specific processes performed in the traditional DSP digital receiver must be programmed and downloaded into the DSP and other receiver elements. Implementing such a DSP receiver at variable data rates up to 10 Gbps is an expensive and complex process, and requires prime power on the order of several hundreds of Watts.
In view of the above, it is advantageous to have a digital receiver that consumes less power than conventional designs and that is programmable to accommodate a large variety of signal waveforms and data rates. It is therefore an objective of the present invention to provide for programmable digital baseband receivers employing programmable complex threshold detectors and threshold interpreters that implement coherent signal detection, automatic gain control and symbol decision processing to permit processing of a large number of bandwidth efficient QAM signal formats, and the like.